3 * lock.c -- routines to lock/unlock files
7 * This code is Copyright (c) 2002, by the authors of nmh. See the
8 * COPYRIGHT file in the root directory of the nmh distribution for
9 * complete copyright information.
12 /* Modified by Ruud de Rooij to support Miquel van Smoorenburg's liblockfile
14 * Since liblockfile locking shares most of its code with dot locking, it
15 * is enabled by defining both DOT_LOCKING and HAVE_LIBLOCKFILE.
17 * Ruud de Rooij <ruud@debian.org> Sun, 28 Mar 1999 15:34:03 +0200
21 #include <h/signals.h>
24 #ifdef TIME_WITH_SYS_TIME
25 # include <sys/time.h>
28 # ifdef TM_IN_SYS_TIME
29 # include <sys/time.h>
42 # include <sys/file.h>
45 #if defined(LOCKF_LOCKING) || defined(FLOCK_LOCKING)
46 # include <sys/file.h>
51 #if defined(HAVE_LIBLOCKFILE)
56 char *lockdir = LOCKDIR;
59 /* Are we using any kernel locking? */
60 #if defined (FLOCK_LOCKING) || defined(LOCKF_LOCKING) || defined(FCNTL_LOCKING)
61 # define KERNEL_LOCKING
66 /* struct for getting name of lock file to create */
69 #if !defined(HAVE_LIBLOCKFILE)
75 * Amount of time to wait before
76 * updating ctime of lock file.
80 #if !defined(HAVE_LIBLOCKFILE)
82 * How old does a lock file need to be
83 * before we remove it.
86 #endif /* HAVE_LIBLOCKFILE */
88 /* struct for recording and updating locks */
95 /* top of list containing all open locks */
96 static struct lock *l_top = NULL;
97 #endif /* DOT_LOCKING */
102 #ifdef KERNEL_LOCKING
103 static int lkopen_kernel (char *, int, mode_t);
107 static int lkopen_dot (char *, int, mode_t);
108 static int lockit (struct lockinfo *);
109 static void lockname (char *, struct lockinfo *, int);
110 static void timerON (char *, int);
111 static void timerOFF (int);
112 static RETSIGTYPE alrmser (int);
117 * Base routine to open and lock a file,
118 * and return a file descriptor.
122 lkopen (char *file, int access, mode_t mode)
124 #ifdef KERNEL_LOCKING
125 return lkopen_kernel(file, access, mode);
129 return lkopen_dot(file, access, mode);
135 * Base routine to close and unlock a file,
136 * given a file descriptor.
140 lkclose (int fd, char *file)
147 struct lockinfo lkinfo;
154 buf.l_type = F_UNLCK;
155 buf.l_whence = SEEK_SET;
158 fcntl(fd, F_SETLK, &buf);
166 /* make sure we unlock the whole thing */
167 lseek (fd, (off_t) 0, SEEK_SET);
168 lockf (fd, F_ULOCK, 0L);
172 lockname (file, &lkinfo, 0); /* get name of lock file */
173 #if !defined(HAVE_LIBLOCKFILE)
174 unlink (lkinfo.curlock); /* remove lock file */
176 lockfile_remove(lkinfo.curlock);
177 #endif /* HAVE_LIBLOCKFILE */
178 timerOFF (fd); /* turn off lock timer */
179 #endif /* DOT_LOCKING */
186 * Base routine to open and lock a file,
187 * and return a FILE pointer
191 lkfopen (char *file, char *mode)
196 if (strcmp (mode, "r") == 0)
198 else if (strcmp (mode, "r+") == 0)
200 else if (strcmp (mode, "w") == 0)
201 access = O_WRONLY | O_CREAT | O_TRUNC;
202 else if (strcmp (mode, "w+") == 0)
203 access = O_RDWR | O_CREAT | O_TRUNC;
204 else if (strcmp (mode, "a") == 0)
205 access = O_WRONLY | O_CREAT | O_APPEND;
206 else if (strcmp (mode, "a+") == 0)
207 access = O_RDWR | O_CREAT | O_APPEND;
213 if ((fd = lkopen (file, access, 0666)) == -1)
216 if ((fp = fdopen (fd, mode)) == NULL) {
226 * Base routine to close and unlock a file,
227 * given a FILE pointer
231 lkfclose (FILE *fp, char *file)
238 struct lockinfo lkinfo;
245 buf.l_type = F_UNLCK;
246 buf.l_whence = SEEK_SET;
249 fcntl(fileno(fp), F_SETLK, &buf);
253 flock (fileno(fp), LOCK_UN);
257 /* make sure we unlock the whole thing */
258 fseek (fp, 0L, SEEK_SET);
259 lockf (fileno(fp), F_ULOCK, 0L);
263 lockname (file, &lkinfo, 0); /* get name of lock file */
264 #if !defined(HAVE_LIBLOCKFILE)
265 unlink (lkinfo.curlock); /* remove lock file */
267 lockfile_remove(lkinfo.curlock);
268 #endif /* HAVE_LIBLOCKFILE */
269 timerOFF (fileno(fp)); /* turn off lock timer */
270 #endif /* DOT_LOCKING */
272 return (fclose (fp));
276 #ifdef KERNEL_LOCKING
279 * open and lock a file, using kernel locking
283 lkopen_kernel (char *file, int access, mode_t mode)
287 # ifdef FCNTL_LOCKING
289 # endif /* FCNTL_LOCKING */
291 for (i = 0; i < 5; i++) {
293 # if defined(LOCKF_LOCKING) || defined(FCNTL_LOCKING)
294 /* remember the original mode */
297 /* make sure we open at the beginning */
301 * We MUST have write permission or
302 * lockf/fcntl() won't work
304 if ((access & 03) == O_RDONLY) {
308 # endif /* LOCKF_LOCKING || FCNTL_LOCKING */
310 if ((fd = open (file, access | O_NDELAY, mode)) == -1)
313 # ifdef FCNTL_LOCKING
314 buf.l_type = F_WRLCK;
315 buf.l_whence = SEEK_SET;
318 if (fcntl (fd, F_SETLK, &buf) != -1)
322 # ifdef FLOCK_LOCKING
323 if (flock (fd, (((access & 03) == O_RDONLY) ? LOCK_SH : LOCK_EX)
328 # ifdef LOCKF_LOCKING
329 if (lockf (fd, F_TLOCK, 0L) != -1) {
330 /* see if we should be at the end */
332 lseek (fd, (off_t) 0, SEEK_END);
347 #endif /* KERNEL_LOCKING */
353 * open and lock a file, using dot locking
357 lkopen_dot (char *file, int access, mode_t mode)
361 struct lockinfo lkinfo;
365 if ((fd = open (file, access, mode)) == -1)
369 * Get the name of the eventual lock file, as well
370 * as a name for a temporary lock file.
372 lockname (file, &lkinfo, 1);
374 #if !defined(HAVE_LIBLOCKFILE)
376 /* attempt to create lock file */
377 if (lockit (&lkinfo) == 0) {
378 /* if successful, turn on timer and return */
379 timerON (lkinfo.curlock, fd);
383 * Abort locking, if we fail to lock after 5 attempts
384 * and are never able to stat the lock file.
386 if (stat (lkinfo.curlock, &st) == -1) {
394 /* check for stale lockfile, else sleep */
395 if (curtime > st.st_ctime + RSECS)
396 unlink (lkinfo.curlock);
400 lockname (file, &lkinfo, 1);
404 if (lockfile_create(lkinfo.curlock, 5, 0) == L_SUCCESS) {
405 timerON(lkinfo.curlock, fd);
412 #endif /* HAVE_LIBLOCKFILE */
415 #if !defined(HAVE_LIBLOCKFILE)
417 * Routine that actually tries to create
422 lockit (struct lockinfo *li)
425 char *curlock, *tmplock;
431 curlock = li->curlock;
432 tmplock = li->tmplock;
435 if ((fd = mkstemp(tmplock)) == -1)
438 if (mktemp(tmplock) == NULL)
440 if (unlink(tmplock) == -1 && errno != ENOENT)
442 /* create the temporary lock file */
443 if ((fd = creat(tmplock, 0600)) == -1)
448 /* write our process id into lock file */
449 snprintf (buffer, sizeof(buffer), "nmh lock: pid %d\n", (int) getpid());
450 write(fd, buffer, strlen(buffer) + 1);
456 * Now try to create the real lock file
457 * by linking to the temporary file.
459 fd = link(tmplock, curlock);
462 return (fd == -1 ? -1 : 0);
464 #endif /* HAVE_LIBLOCKFILE */
467 * Get name of lock file, and temporary lock file
471 lockname (char *file, struct lockinfo *li, int isnewlock)
480 if ((cp = strrchr (file, '/')) == NULL || *++cp == 0)
486 snprintf (bp, sizeof(li->curlock), "%s/", lockdir);
487 tmplen = strlen (bp);
492 snprintf (bp, sizeof(li->curlock), "%.*s", cp - file, file);
493 tmplen = strlen (bp);
501 * mmdf style dot locking. Currently not supported.
502 * If we start supporting mmdf style dot locking,
503 * we will need to change the return value of lockname
505 if (stat (file, &st) == -1)
508 snprintf (bp, sizeof(li->curlock) - bplen, "LCK%05d.%05d",
509 st.st_dev, st.st_ino);
512 snprintf (bp, sizeof(li->curlock) - bplen, "%s.lock", cp);
514 #if !defined(HAVE_LIBLOCKFILE)
516 * If this is for a new lock, create a name for
517 * the temporary lock file for lockit()
520 if ((cp = strrchr (li->curlock, '/')) == NULL || *++cp == 0)
521 strncpy (li->tmplock, ",LCK.XXXXXX", sizeof(li->tmplock));
523 snprintf (li->tmplock, sizeof(li->tmplock), "%.*s,LCK.XXXXXX",
524 cp - li->curlock, li->curlock);
531 * Add new lockfile to the list of open lockfiles
532 * and start the lock file timer.
536 timerON (char *curlock, int fd)
541 lp = (struct lock *) mh_xmalloc (sizeof(*lp));
543 len = strlen(curlock) + 1;
545 lp->l_lock = mh_xmalloc (len);
546 memcpy (lp->l_lock, curlock, len);
550 /* perhaps SIGT{STP,TIN,TOU} ? */
551 SIGNAL (SIGALRM, alrmser);
560 * Search through the list of lockfiles for the
561 * current lockfile, and remove it from the list.
567 struct lock *pp, *lp;
572 for (pp = lp = l_top; lp; pp = lp, lp = lp->l_next) {
580 pp->l_next = lp->l_next;
587 /* if there are locks left, restart timer */
594 * If timer goes off, we update the ctime of all open
595 * lockfiles, so another command doesn't remove them.
605 #ifndef RELIABLE_SIGNALS
606 SIGNAL (SIGALRM, alrmser);
609 /* update the ctime of all the lock files */
610 for (lp = l_top; lp; lp = lp->l_next) {
611 lockfile = lp->l_lock;
612 #if !defined(HAVE_LIBLOCKFILE)
613 if (*lockfile && (j = creat (lockfile, 0600)) != -1)
616 lockfile_touch(lockfile);
620 /* restart the alarm */
624 #endif /* DOT_LOCKING */